Plant for producing sanitary hot water

ABSTRACT

The invention relates to a plant for producing sanitary hot water, that comprises a water heater including a tank ( 1 ) containing a fluid to be heated, and a controlled mechanical ventilation system ( 2 ) for extracting air from a dwelling, the controlled mechanical ventilation system ( 2 ) being coupled to a thermodynamic circuit ( 3 ) in which flows a coolant fluid, the thermodynamic circuit ( 3 ) including an evaporator ( 4 ) for exchanging heat with the extracted air, a compressor ( 6 ), an expander ( 8 ) and a condenser ( 7 ) for exchanging heat with the fluid contained in the tank ( 1 ). The ventilation system is equipped with a means for adjusting the flow of extracted air, e.g. based on hygrometry. The compressor ( 6 ) is a variable speed compressor capable of modifying the flow of the coolant fluid.

TECHNICAL FIELD

The invention relates to a plant for producing sanitary hot water.

BACKGROUND

A plant for producing sanitary hot water is intended to supply in particular a single dwelling or group dwellings.

Given the environmental constraints and the high cost of energy, it is necessary to reduce the consumption of different plants in dwellings. The needs of the plant for heating a dwelling have been significantly reduced, especially by the use of new insulation materials, the installation of adapted glazing, and the reduction of thermal bridges during the construction of the building.

Similarly, the needs of a plant intended for the ventilation of the dwelling are significantly reduced by using a double flow ventilation, allowing to recover calories on the extracted airflow in order to transfer them to the injected airflow or by using a modulated ventilation, the operation of which is limited to actual and functional needs, for example, on the hygrometry rate inside the dwelling.

Presently, it is observed that, in the “low consumption” type homes, the plant intended for producing sanitary hot water is that which uses most of the energy.

It is therefore evident that it is necessary to reduce the energy needs of this type of plant.

For this purpose, it is known to use a plant producing sanitary hot water with a water heater including a tank within which is stored fluid to be heated, and a controlled mechanical ventilation system intended to extract air from a dwelling, the controlled mechanical ventilation system being coupled to a thermodynamic circuit within which flows a coolant fluid, the thermodynamic circuit having an evaporator for exchanging heat with the extracted air, a compressor, an expander and a condenser for exchanging heat with the fluid contained in the tank.

Such a plant is generally designated by the term “thermodynamic water heater on the extracted air”.

Such a type of plant allows recovering part of the heat of the extracted air and transferring it to the fluid contained in the tank of the water heater, through the thermodynamic circuit and heat exchangers formed by the evaporator and the condenser.

This type of plant requires airflow substantially constant and significant in order to heat the water in the tank. Indeed, in the case where the airflow is reduced, the performance of the plant deteriorates and appears the risk of icing in the extracted air.

In this case, either the plant is stopped automatically and goes into so-called security or the occurrence of the icing phenomena risks damaging the plant, in particular the ventilation system.

Accordingly, the ventilation system used by this type of plant is necessarily a constant flow system, the flow value being of a sufficient value to ensure the operation of the plant. Such an extracted airflow creates significant heat losses in the dwelling.

Another disadvantage of this type of plant is to operate only on starting or on stopping, the hysteresis of operation being monitored through a temperature probe for measuring the temperature of the distributed sanitary hot water. So that, when the temperature of the sanitary hot water is below a predetermined low value, the compressor is started so that the water contained in the tank is heated. When the water temperature exceeds a predetermined high value, the compressor is stopped.

Such an operation creates non-optimised energy consumption by the compressor.

BRIEF SUMMARY

The invention attempts to remedy these drawbacks by providing a plant for producing sanitary hot water by optimising the recovery of thermal energy available in the extracted air, while limiting the energy consumption required for the operation of the plant.

To this end, the invention relates to a plant for producing sanitary hot water of the aforesaid type, characterised in that the ventilation system is equipped with means for adjusting the extracted airflow, for example based on the hygrometry, and in that the compressor is a variable speed compressor, capable to modify the flow of coolant fluid.

In this way, the extracted airflow may be modulated or adjusted according to the ventilation needs of the building.

In addition, use of a variable speed compressor, generally called compressor of the “inverter” type, allows adjusting the flow of the coolant fluid based on the available heat or being able to be drawn from the extracted air, so as to ensure the proper functioning of the plant. This is how, for example, a reduction of the flow of extracted air is followed by a reduction in compressor speed and hence a decrease in the amount of heat taken from the extracted air, in order to avoid any icing phenomenon.

Furthermore, the adjustment of the compressor speed allows enabling to operate it at low speed whenever possible, so that the energy consumption linked to the operation of the compressor is greatly reduced.

According to a characteristic of the invention, the plant includes means providing information on the extracted airflow, interacting with the compressor to adjust the flow of the coolant fluid in the corresponding circuit based on the measured airflow.

Measurement of airflow provides direct information on the amount of available energy that may be drawn from the extracted air and then transferred to the fluid contained in the tank of the water heater.

Advantageously, the plant includes at least one extracted air temperature probe, located downstream of the evaporator in the direction of air and interacting with the compressor to adjust the flow of coolant fluid into the corresponding circuit according to the temperature of the measured air.

Measurement of the extracted air temperature provides indirect information on the amount of energy available that may be drawn. Indeed, the extracted air temperature, downstream of the evaporator is as much further reduced as the remaining energy contained in the extracted air is low.

According to another possibility of the invention, the temperature probe could be located upstream of the evaporator.

According to a possibility of the invention, the invention includes at least one temperature probe, capable of measuring the temperature of the fluid contained in the water heater tank, interacting with the compressor so as to adjust the flow of the coolant fluid into the corresponding circuit, based on the temperature of the measured fluid.

Measurement of the temperature of the fluid in the tank allows obtaining information on the status of the sanitary hot water reserve and allows to maximise the time and speed of the operation of the compressor.

Preferably, the plant includes a plurality of temperature probes, located at different tank levels, so as to measure the temperature of a plurality of fluid layers contained in the tank.

According to a characteristic of the invention, the means for measuring the extracted airflow, the temperature probe of the extracted air and/or the temperature probe of the fluid are connected to a central control unit designed to adjust the compressor speed based on measured airflow, of the temperature of the measured air and/or the temperature of the measured fluid.

According to one embodiment, the condenser is located inside the water heater tank so as to exchange directly heat with the fluid contained in the tank.

According to another embodiment, the plant includes a secondary circuit of heat exchange within which flows a heat transfer fluid passing through the condenser to exchange heat with the coolant, the secondary circuit further includes a heat exchanger located within the water heater tank, so as to exchange heat with the fluid in the tank.

Preferably, the heat exchanger of the secondary circuit is a coil.

According to a characteristic of the invention, the controlled mechanical ventilation system includes at least one air vent intended for the passage of extracted air, the adjusting means for the extracted airflow including adjusting means for the opening of the air vent.

Thus, when it is necessary to have a significant extracted airflow, the air vent may be opened fully. This is particularly the case during the operation phases of the thermodynamic circuit compressor, in order to maximise heat exchanges between the extracted air and the fluid to be heated contained in the tank.

Advantageously, the controlled mechanical ventilation system includes at least one first air vent intended for the passage of extracted air, the adjusting means of the extracted airflow including at least one second air vent and control means designed to control the opening and closing of the second air vent.

The second air vent plays a similar role to that described above. Indeed, when it is desired to increase the extracted airflow, it is sufficient to open the second air vent. In order to improve the comfort of the residents, it may also be useful to increase the extracted airflow during summer, so as to over ventilate a room of the home, especially at night.

Vice versa, should an over ventilation be avoided, closing of the second air vent will cause reducing the extracted airflow.

The second air vent may be located at a heat source, for example behind a refrigerator, in order to increase the performances of the plant for producing sanitary hot water.

The second air vent may also be located in a living room so as to over ventilate the said room during summer and during the night, in order to improve comfort for residents.

BRIEF DESCRIPTION OF THE DRAWINGS

In any case, the invention will be better understood from the description which follows, with reference to the attached schematic drawing showing, by way of non limiting examples, two embodiments of this plant for producing sanitary hot water.

FIG. 1 is a schematic view of a first embodiment of the invention;

FIG. 2 is a view corresponding to FIG. 1, of a second embodiment of the invention;

FIG. 3 is a diagram showing, for a first mode of operation, the power supplied by the plant compressor based on time, compared with a plant of the prior art;

FIG. 4 is a diagram showing, for the first mode of operation, the cumulated consumption of the compressor based on time;

FIGS. 5 and 6 are diagrams corresponding to those of FIGS. 3 and 4, for a second mode of operation of the plant.

DETAILED DESCRIPTION

FIG. 1 shows a first embodiment of a plant for producing sanitary hot water according to the invention.

The latter includes a water heater comprising a tank 1 within which is stored fluid to be heated, and a controlled mechanical ventilation system 2 intended for extracting air from a dwelling.

The controlled mechanical ventilation system 2 is equipped with means for adjusting extracted airflow, for example based on the hygrometry, and is coupled to a thermodynamic circuit 3 within which flows a coolant fluid.

The thermodynamic circuit 3 includes successively, in the direction of flow of the coolant fluid, an evaporator 4 for exchanging heat with the extracted air 5, a compressor 6, a condenser 7 for exchanging heat with the fluid contained in a tank 1, and an expander 8. The flow direction of the coolant fluid is shown by arrows. In addition, the phase and the pressure of the coolant fluid are identified by references VBD (Low Steam Pressure), VHP (High Steam Pressure), LHP (Liquid High Pressure) and LBP (Liquid Low Pressure).

More specifically, the compressor 6 is a variable speed compressor, capable of modifying the flow of the coolant fluid. In addition, the condenser 7 is located inside the water heater tank 1, so as to exchange directly heat with the fluid contained in the tank 1.

The plant also includes means 9 for measuring the flow of extracted air, a temperature probe 10 for the extracted air, located downstream of the evaporator 4 in the direction of airflow, and a plurality of temperature probes 11, located at different levels of the tank 1 and capable of measuring the temperature of a plurality of layers of the fluid contained in the tank 1.

The means 9 for measuring airflow, the air temperature probe 10 and/or the fluid temperature probes 11 are connected to a central control unit 12 designed to adjust the speed of the compressor 6 based on the measured airflow, the measured air temperature and/or the measured fluid temperature.

In a second embodiment shown in FIG. 2, the condenser 7 is located outside the tank. The plant also includes a secondary circuit 13 of heat exchange, equipped with a pump 14 and within which flows a coolant fluid. The secondary circuit 13 passes through the condenser 7 so as to exchange heat with the coolant fluid. The secondary circuit 13 also includes a heat exchanger 15 in the shape of a coil, located within the tank 1 of the water heater, so as to exchange heat with the fluid contained in the tank 1.

The diagram in FIG. 3 includes a first curve, referenced (1), showing the operation of a plant of the classical thermodynamic water heater type, and a second curve, referenced (2), showing the operation of the plant according to the invention.

This Figure shows the operation of the aforementioned plants for a constant extracted airflow of Q1 value.

In the case of the conventional plant (curve 1), the compressor is started in the time interval between t0 and t1, the fixed-speed compressor power of this plant being equal to P1.

In the case of the plant according to the invention (curve 2), it is possible to run the compressor 6 at a slower speed for a longer period of time (t0 and t2), with a better performance.

Power P2 supplied by the variable speed compressor 6 is then reduced.

Consequently, as derived from FIG. 3, the cumulative consumption C of the variable speed compressor (curve 2) is reduced, compared with the accumulated consumption of the fixed speed compressor (curve 1) used by the plant of the prior art.

FIG. 5 shows another mode of operation wherein the extracted airflow Q1 during the time interval t3 to t4 is reduced and equal to Q2 during the time interval t4 to t5. This mode of operation is that of the modulated ventilation system, wherein the extracted airflow is adjusted based on the needs.

In the case of a conventional plant (curve 1), the plant operates during the time interval t3 to t4, when the extracted airflow is maximum. When the extracted airflow falls, in the time interval t4 to t5, the plant must be stopped in order not to generate any icing in the extracted air. Consequently, as shown in FIG. 5, the compressor is stopped and the water contained in the tank cannot be heated during this period.

On the contrary, in the case of a plant according to the invention (curve 2), the compressor 6 may for example operate at full speed during the time interval t3 to t4, then at a reduced speed during the time interval t4 to t5, so as to avoid problems due to icing. The performance of the plant is therefore increased. In addition, consumption of the compressor 6 operating at reduced speed is also reduced.

It will hence be observed that the plant according to the invention is capable to operate in combination with a modulated ventilation system 3. It is recalled that such a system allows limiting thermal losses due to hot air extraction, these losses being also limited by the fact that the plant according to the invention allows to recover part of the heat from the extracted air, and this, regardless of the extracted airflow.

It is therefore evident that the invention allows optimising the recovery of thermal energy available in the extracted air.

According to one embodiment, the controlled mechanical ventilation system includes one or more air vents intended for passing the extracted air, adjusting means allowing adjusting the opening of the said air vents.

According to another embodiment, the controlled mechanical ventilation system includes at least a first air vent, intended for the passage of the extracted air during normal operation, and at least a second air vent. Control means designed to control the opening and the closing of the second air vent allow passing from a state of normal operation wherein the extracted air passes only through the first air vent in a state called of over-ventilation wherein air is extracted both through the first and the second air vents.

It is thus possible to vary the extracted airflow based in particular on the operating cycle of the thermodynamic circuit and the thermodynamic conditions, in order to improve the performances of the plant for producing sanitary hot water. It is in this way that, in order to optimise the exchange of heat between the extracted air and the fluid to be heated, it is useful to have a more significant extracted airflow. It goes without saying that the invention is not limiting to the embodiments of this plant, described above by way of non limiting examples, but it embraces, on the contrary, all the variants. 

1. Plant for producing sanitary hot water including: a water heater comprising a tank within which is stored fluid to be heated, and a controlled mechanical ventilation system intended for extracting air from a dwelling, the controlled mechanical ventilation system being coupled to a thermodynamic circuit within which flows a coolant fluid, the thermodynamic circuit including an evaporator for exchanging heat with extracted air, a compressor, an expander, and a condenser for exchanging heat with fluid contained in the tank, wherein the ventilation system is equipped with means for adjusting the extracted airflow based on hygrometry, and wherein the compressor is a variable speed compressor, capable of modifying a flow of coolant fluid.
 2. Plant according to claim 1, further comprising means providing information on the extracted airflow interacting with the compressor so as to adjust a flow of coolant fluid in the corresponding circuit based on a measured airflow.
 3. Plant according to claim 2, further comprising at least one temperature probe of the extracted air, located downstream of the evaporator in a direction of the airflow, and interacting with the compressor so as to adjust a flow of coolant fluid in the corresponding circuit based on temperature of the measured air.
 4. Plant according to claim 3, further comprising at least one temperature probe, capable of measuring temperature of the fluid contained in the tank of the water heater, interacting with the compressor so as to adjust a flow of the coolant fluid in the corresponding circuit, based on temperature of the measured fluid.
 5. Plant according to claim 4, further comprising a plurality of temperature probes located at different levels of the tank so as to measure temperature of a plurality of layers of the fluid contained in tank.
 6. Plant according to claim 4, wherein the means for providing information on the extracted airflow, the temperature probe of the extracted air and/or the temperature probe of the fluid are connected to a central control unit designed to adjust a speed of the compressor based on the measured airflow, the temperature of the measured air and/or the temperature of the measured fluid.
 7. Plant according to claim 1 wherein the condenser is located inside the tank of the water heater, so as to exchange heat directly with the fluid contained in the tank.
 8. Plant according to claim 1, further comprising a secondary circuit of heat exchange inside of which flows a coolant fluid, passing through the condenser so as to exchange heat with the coolant fluid, the secondary circuit further including a heat exchanger located inside the tank of the water heater, so as to exchange heat with the fluid contained in the tank.
 9. Plant according to claim 8, wherein the heat exchanger of the secondary circuit is a coil.
 10. Plant according to claim 1, wherein the controlled mechanical ventilation system includes at least an air vent intended for passage of extracted air, the means for adjusting the extracted airflow including means for adjusting an opening of the air vent.
 11. Plant according to claim 1, wherein the controlled mechanical ventilation system includes at least one first air vent intended for passage of extracted air, means for adjusting the extracted airflow including at least a second air vent and control means designed to control opening and closing of the second air vent. 